The present invention is directed to a feeder device on a sewing machine with a material feeder which reaches through the stitch plate from below and is driven by a lift- and thrust rocker along a path made up of four phases.
With feeder devices known from Swiss Pat. No. 342,456, for example, a cam controls, in each case, the upward or upwardly directed lifting motion and the forward or backward thrust movement of the material feeder, whereby movement is transferred from the cams through the rocker arms and lift and thrust rockers, securely connected to these and engaging on the support of the material feeder. This drive method moves the material feeder in a nearly parallelogram-shaped path (with stitch lengths&gt;zero). However, the transitions between the straight line lift segment and the straight line horizontal thrust movement of the effective part, i.e. lying above the stitch plate, of the material feeder movement path are relatively long arcs. This is a result of the partial superimposition of the lift and pivot movements and the swinging of the material feeder support around the horizontal axis of the thrust rocker. However, not only the movement effectiveness of the material feeder in these transition curves of the material feeder path is reduced, making it impossible to exactly determine the beginning and end of transport, but the thrust lengths with forward and reverse stitches also do not correspond exactly. The effective thrust length should, however, be exactly identical in both directions regardless of the selected material feed direction. The limited space within the sewing machine arm makes it necessary to cramp the components of the feeder device, which is also disadvantageous to its movement path, because the suspension point of the material feeder support to the thrust rocker must necessarily lie very close to the material feeder. Indeed, an attempt has already been made, e.g. according to the German Offenlegungsschrift No. 19 07 749, to come up with a feeder device with a straight line movement path. This device is very complicated and due to its construction can only be built into industrial chain stitch sewing machines.
These disadvantages are eliminated by the present invention, which includes a feeder device of the type mentioned which, on the one hand, imparts to the material feeder in the effective area, an approximately rectangular path with very narrow curve transitions between the horizontal thrust segment and the adjacent, at least approximately vertical lift segment and which, on the other hand, is simply constructed and space saving so that it can be used for home, free-arm sewing machines.
To this end the feeder device according to the present invention is characterized by the fact that the support of the material feeder is arranged on an intermediate rocker which, in turn, is rotatingly attached to the thrust rocker, whereby the horizontal rotation axis of the support is arranged on the intermediate rocker at a distance from the rotational axis of the intermediate rocker disposed parallel thereto. The intermediate rocker is, along with the support, set in a vertically oscillating motion and rotated around its rotational axis by a direct connection with the lift rocker, which, by means of the proper correction, provides the movement path of the material feeder, made up of the lift and thrust movements transferred to the support consisting of a lift and a thrust component, at least an approximately rectangular form in the effective area. A particularly advantageous arrangement consists in the configuration wherein the horizontal rotational axis of the support is arranged on the intermediate rocker, nearly vertically, at a distance below the rotational axis connecting the intermediate rocker with the thrust rocker.
Due to the intermediate rocker provided in the present invention, the mentioned transition curves between the horizontal and at least the approximately vertical movement segments in the effective area of the movement path of the material feeder is narrow enough that the horizontal upward movement segment, relative to the maximal thrust length of the material feeder, is not only very large, but is practically identical in both feed directions.